I Want a Smart Thermostat but Don't Have a C Wire - What Do I Do?

June 09, 2021

When you’re wanting ways to decrease heating and cooling costs, upgrading to a smart thermostat is a smart idea. These devices learn your favorite temperatures and routine and then make an energy-efficient schedule to match. What’s even better is that you can change and keep an eye on your settings from almost anywhere with your phone, whether you’re sitting in bed or away from home. (You might even be able to receive a free smart thermostat depending on rebate programs from your utility company in Greater Richmond.)

Most of the time, adding a smart home thermostat with the support of Herman Allen Plumbing, Heating & Cooling is a simple task if you have a more modern house. But what if your house is older or doesn’t have the correct wiring? Can you still add a smart thermostat without C wire? We’ll help you figure out the process so you can select the correct thermostat and receive energy savings for years to come.

What Is a C Wire and What Does It Do on a Thermostat?

The majority of programmable thermostats run on batteries. When you’re making the move to a smart thermostat, you’ll discover that many have to have a C wire, or common wire, for power. Without this wire, your new thermostat could cause your heating and cooling system to have malfunctions.

You can find out if you have a C wire by doing the following:

  1. Switch off power to the thermostat at the breaker.
  2. Take off the thermostat and find the wiring.
  3. If there are five or six multicolored wires, you have what’s required for a smart thermostat. You might be wondering what color is the C wire on a thermostat—and the answer to that is often blue.
  4. If there are three or four thin multicolored wires, you’re nearly there. Make sure the C wire isn’t tucked in the wall. If you can’t find one, we may be able to put in one for you or you may be able to operate your new thermostat without one.
  5. If you have two thick wires, you may be able to run a smart thermostat with an adaptor just for high-voltage systems. Or you may be able to operate a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring is incompatible and you don’t want to install new wiring.

Do Nest or ecobee Need a C Wire?

Two of the top brands are the Nest smart thermostat and ecobee smart thermostat. If you have two to four wires, these thermostats may be a match for your needs.

Nest says its thermostats are made to consume minimal power and can typically share it with your home comfort system. However, you may need to have a professional like Herman Allen Plumbing, Heating & Cooling put in a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re experiencing power problems or a battery that’s constantly drained.

ecobee works with 24-volt systems (ones with three to six thermostat wires) and includes a C wire adaptor. So, you’re taken care of if you don’t have a thermostat C wire.

Depend on Herman Allen Plumbing, Heating & Cooling for Your Smart Thermostat Installation Needs

At Herman Allen Plumbing, Heating & Cooling, we’re always seeking approaches to keep you cozier while keeping utility bills reasonable. If you want to know more about upgrading to a smart thermostat without a C wire, give us a call at 804-302-6657. We can help you choose the right model for your house and even install new wiring if necessary.